The high temperature behavior of superalloys exposed to sodium chloride: II. corrosion
- PDF / 1,950,649 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 72 Downloads / 144 Views
IN the p r e c e d i n g paper,1
the effect of high t e m p e r a t u r e e x p o s u r e to NaC1 on the m e c h a n i c a l p r o p e r t i e s of s u p e r a l l o y s (Inconel 718, I n c o n e l 625, R e n e ' 41, Haynes 188, T D - N i C r ) has b e e n studied. R e s i d u a l m e c h a n i c a l p r o p e r t i e s , as d e t e r m i n e d by a p o s t e x p o s u r e t e n s i l e t e s t , w e r e found to be s e r i o u s l y d e g r a d e d , the a m o u n t of d e g r a d a t i o n being dependent on the p a r t i a l p r e s s u r e of oxygen in the e n v i r o n m e n t . C r e e p r a t e s w e r e i n c r e a s e d up to t h r e e o r d e r s of magnitude in the p r e s ence of NaCl at t e m p e r a t u r e s a r o u n d 1000~ In o r d e r to obtain i n f o r m a t i o n r e g a r d i n g c o r r o s i o n r a t e s of the v a r i o u s s u p e r a l l o y s , the c o m p o s i t i o n of c o r r o s i o n p r o d u c t s , and the effect of oxygen, e x p e r i m e n t s w e r e a l s o c a r r i e d out in m o l t e n NaC1. R e s u l t s of these i n v e s t i g a t i o n s a r e r e p o r t e d in this c o m m u n i cation. In m o l t e n NaC1, it is p o s s i b l e to study the e l e c t r o c h e m i c a l b e h a v i o r of alloys by r e c o r d i n g p o l a r i z a tion c u r v e s , as has been done with g r e a t s u c c e s s in a q u e o u s m e d i a . T h e s e e l e c t r o c h e m i c a l t e c h n i q u e s have r e c e n t l y b e e n e m p l o y e d by R a h m e l 2 in a study of i r o n and s e v e r a l s t e e l s in a eutectic a l k a l i sulfate m e l t , and by Baudo, T a m b a , and B o m b a r a s in an e l e c t r o c h e m i c a l i n v e s t i g a t i o n of c o r r o s i o n of f e r r i t i c s t e e l s in m o l t e n s u l f a t e s . J a n z and Conte 4 conducted p o t e n t i o s t a t i c p o l a r i z a t i o n s u t d i e s on s t a i n l e s s s t e e l in fused c a r b o n a t e s , while Devyatkin and Ukshe s studied the b e h a v i o r of i r o n in m o l t e n c h l o r i d e s . No e l e c t r o c h e m i c a l s t u d i e s in m o l t e n s a l t s have b e e n r e p o r t e d p r e v i o u s l y for the a l l o y s of i n t e r e s t in the p r e s e n t study. In this i n v e s t i g a t i o n the c o r r o s i o n r a t e s of the a l l o y s w e r e d e t e r m i n e d f r o m weight loss data, while the c o r r o s i o n p r o d u c t s w e r e a n a l y z e d by m a s s s p e c t r o s c o p y , a t o m i c a b s o r p t i o n s p e c t r o s c o p y , and X - r a y d i f f r a c t i o n . M a s s s p e c t r o s c o p y was a l s o used to detect diffusion of s o d i u m and c h l o r i n e into the bulk of the m e t a l s . P o l a r i z a t i o n c u r v e s have b e e n obtained by p o t e n t i o s t a t i c measurements.
F. MANSFELD, N. E. PATON, and W. M. ROBERTSON are Members of the Technical Staff, North American Rockwell Science Center, Thousand Oaks, Calif. 91360. Manuscript submitted March 13, 1972. METALLURGICALTRANSACTIONS
E X P E R I
Data Loading...
